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Re: [css3-conditional] What does @supports return when the OS prevents the support?

From: L. David Baron <dbaron@dbaron.org>
Date: Fri, 11 Jan 2013 12:19:21 -0800
To: Sylvain Galineau <sylvaing@microsoft.com>
Cc: James Nurthen <james.nurthen@oracle.com>, CSS WG <www-style@w3.org>
Message-ID: <20130111201921.GA30397@crum.dbaron.org>
On Thursday 2013-01-10 19:38 +0000, Sylvain Galineau wrote:
> 
> [James Nurthen:]
> > 
> > When the CSS processor "supports" a value BUT the OS prevents the support
> > from actually occurring what would be the result?
> > For example. Would
> > @supports (background-color: #CCC) return true or false when running in
> > Windows High Contrast mode where background colours are not applied.
> > 
> > It would be very useful if this would return false - so this situation
> > could be detected in CSS and appropriate styles applied.
> > 
> What would you expect when the document is being printed and the color might 
> either end up in a shade of grey or the UA might disable backgrounds entirely 
> when printing based on a user setting? 
> 
> Whether the UA supports a particular property-value pair and what the target 
> media does with this same feature are orthogonal in my mind.

I tend to agree with Sylvain here.  I think that there are other
parts of CSS (in particular, the cascade) that are designed for the
interaction of author and user requirements.  There also may be
substantive cases where the user would like to override the author
without the author knowing about it.  I'm inclined to leave
@supports limited to describing the capabilities of the
implementation rather than the user's configuration of it.

(I'm distinguishing user configuration that's intended for end users
from configuration that allows developers to try out experimental
features and thus change the capabilities of the implementation.)

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂
Received on Friday, 11 January 2013 20:19:53 GMT

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